Biology subjects

Chakrabarty, Y.

Publications and source records attributed to Chakrabarty, Y..

3 recordsLinked to original sources

bioRxiv2020

GW182 Proteins Restrict Extracellular Vesicle Mediated Selective Export of Used miRNAs In Mammalian Cancer Cells

MicroRNAs are small regulatory RNAs of relatively long half-life in non-proliferative human cells. However, in cancer cells the half-lives of miRNAs are comparatively short. To understand the mechanism of rapid miRNA turn over in cancer cells, we explored the effect of "usage" of specific miRNAs for translation repression of their targets on the abundance of that miRNA. We have noted an accelerated extracellular vesicle mediated export of "used" miRNAs in mammalian cells and the miRNA-export process get retarded by Ago2 interacting protein GW182B. The GW182 group of proteins are localized to GW182 Bodies or RNA Processing Bodies in mammalian cells and GW182B dependent retardation of miRNA export depends on GW-body integrity and is independent of HuR mediated auxiliary pathway of miRNA export. Our data thus support existence of a HuR independent pathway of miRNA export in human cells that can be targeted to increase cellular miRNA levels in cancer cells to induce senescence. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/294488v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1d6e30dorg.highwire.dtl.DTLVardef@d4ab06org.highwire.dtl.DTLVardef@282ad4org.highwire.dtl.DTLVardef@113ef76_HPS_FORMAT_FIGEXP M_FIG C_FIG Key PointsO_LIUsage of miRNA is proportional with its export and turnover C_LIO_LIGW182 proteins cause phase separation of Ago2 to P-bodies and restrict miRNA export via extracellular vesicles (EVs) C_LIO_LIHuR driven auxiliary path of miRNA export is independent of GW182 controlled main path of miRNA exclusion C_LI

molecular biology↗

bioRxiv2020

Mitochondria Controlled mTORC1 Activation Compartmentalizes Translation Initiation Factor eIF4E to Augment Intracellular Trafficking and Extracellular Export of miRNA in Mammalian Cells

Defective intracellular trafficking and export of miRNAs has been observed in senescent mammalian cells having impaired mitochondrial potential. Similar to what happens in senescent cells, Uncoupling Protein 2 mediated depolarization of mitochondrial membrane potential results in progressive sequestration of miRNAs with polysomes and lowered release of miRNAs through extracellular vesicles. Supporting importance of mitochondrial membrane potential on miRNAs fate determination, impaired miRNA-trafficking process in growth retarded human cells has been found to be reversed in presence of Genipin an inhibitor of Uncoupling Protein 2. Mitochondrial detethering of endoplasmic reticulum in mitochondria depolarized cells, found to be responsible for defective compartmentalization of translation initiation factor eIF4E to ER attached polysomes. It causes retarded translation process of target mRNAs with rER attached polysomes to ensure reduced intracellular trafficking and extracellular export of miRNAs. We have identified a reduced activity of mTORC1 complex in mitochondria defective cells to cause reduced phosphorylation of eIF4E-BP1 to cause retarded eIF-4E targeting to ER attached polysome. Cumulatively, these data suggest intricate involvement of mitochondrial membrane potential and dynamics to determine stability of miRNAs in mammalian cells by affecting sub-cellular locations and export of miRNPs by affecting mTORC1 complex, the regulator of the protein translational machinery. Significance statementHow the reduced mitochondrial activity in growth retarded cells causes defective miRNA export is an open question. Mitochondrial defects induces a retarded subcellular miRNP trafficking in human cells to cause an upregulation in cellular miRNA content by reducing extracellular vesicle-mediated export of miRNA. We have identified a defective compartmentalization of translation initiation factor eIF4E in mitochondria-ER detethered mammalian cells to cause the retarded intracellular miRNA movement and export Activity of mTORC1 complex, a key regulator of protein translation in mammalian cells, is found to be responsible for ER-compartmentalization of eIF4E. mTORC1 activity reduction in growth retarded and mitochondria detethered cells influences the cell fate by acting on miRNA-mRNA axis. This is a unique way how mitochondrial activity is linked with protein translation and gene repression control in mammalian cells.

molecular biology↗

bioRxiv2019

Plasma membrane damage removal by F-actin-mediated shedding from repurposed filopodia

Repairing plasma membrane damage is vital to eukaryotic cell survival. Membrane shedding is thought to be key to this repair process, but a detailed view of how the process occurs is still missing. Here we used electron cryotomography to image the ultrastructural details of plasma membrane wound healing. We found that filopodia-like protrusions are built at damage sites, accompanied by retraction of neighboring filopodia, and that these repurposed protrusions act as scaffolds for membrane shedding. This suggests a new role for filopodia as reservoirs of membrane and actin for plasma membrane damage repair. Damage-induced shedding was dependent on F-actin dynamics and Myo1a, as well as Vps4B, an important component of the ESCRT machinery. Thus we find that damage shedding is more complex than current models of simple vesiculation from flat membrane domains. Rather, we observe structural similarities between damage-mediated shedding and constitutive shedding from enterocytes that argue for conservation of a general membrane shedding mechanism.

cell biology↗